SSP1492传感器平台芯片应用研究

用SSP1492智能传感器平台芯片与固定电阻或电容构成RC/RL振荡器,将传感器输出信号调制成频率信号,通过测量频率变化解算器件的变化量,进而完成数据采集.以工程中常见的惠斯通全桥传感器为测量对象,讨论了多通道数据采集系统设计.实验表明,SSP1492适合多种类型传感器接入,具有可扩展的采样精度和较高采样速率,能简化测试系统设计方案.     

变频技术在泵与风机系统中应用的节能分析

根据泵与风机在不同工况下运行的性能与特点，分析了变流量运行时，泵与风机流量、扬程(压头)、功率与转速间的关系。介绍了变频器在泵与风机调速上的应用现状，及使用变频器变频调速与挡板节流对比，阐述了变频调速节能原理及经济效益。提出了变流量运行时，泵与风机应采用变频技术，合理配备，并举例分析比较了电厂鼓风机采用变频调节时的特性、耗能情况及其经济性。     

我国北方重点煤电基地发展伴生的水资源压力分析

鉴于煤电基地的快速扩张会给区域水资源保障带来极大的压力,运用生命周期评价方法计算了2006～2015年我国北方九大煤电基地煤炭生产和火力发电的水足迹,提出了虚拟水流出伴生的水资源压力指数,评价了煤电虚拟水外送给当地水资源系统造成的压力,分析了未来煤电基地发展的水资源适配性。结果表明,九大煤电基地煤炭生产和火力发电的年均水足迹为13.4×108 m3,占当地淡水资源可用总量的22.8%,煤炭和电力外送伴生的虚拟水流出总量持续增加,增长率为3 031.9×104 m3/a,近10年来,水资源压力指数呈现上升趋势,六个煤电基地达到中度压力等级,造成巨大的水资源压力;2020年,九大煤电基地总水足迹为15.7×108 m3,区域可供给煤电基地的水资源量为11.9×108 m3,只有晋北和准东的水资源满足未来基地扩张需要;晋中、晋东、陕北和鄂尔多斯通过优化调度等增加区域可供水量后可以满足未来生产需要;宁东和哈密发展所需的水资源与供给能力严重不适配,应调整发展战略,保障基地用水安全。     

电厂锅炉风机的节能分析

从风机在电厂中的应用现状着手,分析了电厂风机的节能途径。通过对风机的几种变速装置的经济性分析,得出选用变频调速装置节能是非常有效的,同时也为其它风机行业高效率利用能源提供了相关依据。     

采用内燃发电车进行SS4型电力机车出厂试验的探索与实践

通过对三相发电机改为单相发电机的运行有关问题分析 ,探索了一种在内燃发电车上采用柴油机驱动单相同步交流发电机进行恒压、恒频发电 ,为SS4 型电力机车变压器的次边绕组供电 ,使原边产生 2 5kV电力机车供电电压 ,在哈大铁路没有供电以前 ,借助大连—瓦房店区间的铁路 ,作为一种变通办法成功地完成了配属郑州铁路局和沈阳铁路局的 2 8台SS4 型电力机车出厂试验。     

电压环对光伏虚拟同步机系统稳定性的影响

传统的新能源发电设备不具备调频调压能力,为解决这一问题,已有研究提出多种针对光伏逆变电源的稳压与电压穿越策略。在此基础上,为进一步提升光伏电源的调频、孤网运行等方面的能力,有学者提出多种类型的虚拟同步发电机(virtual synchronous generator,VSG)控制策略。VSG控制系统中是否存在电压环是区别不同VSG策略的主要特征之一。目前鲜有研究分析VSG控制系统中的电压环对光伏VSG并网稳定性的影响。为补缺这方面的研究,首先对引入和未引入电压环的2种光伏VSG进行小信号建模,通过计算2种VSG模型的特征根,分析电压环及其参数对系统各种潜在振荡模态的影响,尤其对可能诱发高频谐振和次同步振荡的模态进行分析。在此基础上,研究电压环对光伏VSG并网适应性和频率支撑能力的影响。研究结果表明,在电压等级较低、强度较弱的电网中,光伏VSG控制系统中宜引入电压环。     

光伏电站快速频率响应技术研究及应用

随着大容量高比例的新能源集中接入电网,电源结构发生较大变化,电网可用的快速频率响应资源逐步减少,同时大规模新能源基地通过特高压直流外送规模不断扩大,若出现大功率直流闭锁将对电网频率安全造成严重威胁,电网的调频压力及安全运行风险不断增大,亟需新能源参与电网快速频率响应,提升大电网频率风险防控水平。介绍了新能源电站快速频率响应性能要求,面向已有或新建的光伏电站,提出了快速频率响应典型方案,开发了新能源电站一体化控制系统,并在光伏电站开展了示范应用,实现了电站AGC/AVC和快速频率响应功能的集成,达到了光伏电站对电网频率和电压主动支撑的目的。     

排气消声器声场的有限元法分析

本文对S195柴油机的排气噪声进行了详细试验和理论研究。通过试验测量了S195柴油机的排气噪声频谱,并且对采用不同膨胀比消声器的消声效果进行了试验研究。此外,研究了不同穿孔板位置对简单膨胀腔消声器排气噪声的影响。运用有限元方法对消声器的声场进行分析,并与试验结果对比。由于对计算模型进行了简化,所以计算结果与试验结果有差异,但是两者的趋势是一致的。     

我国海上“风电三峡”及非并网风电应用系统开发建议

位于长三角地区的浅海辐射沙洲风能资源十分丰富,而且具有地质条件优越,灾害性气象概率低,没有主航道和大型地下线缆,地处电力负荷中心,高新技术产业基础好,人才基础和资本市场发育良好,已具备理论、技术和实践基础等优势,非常适合发展大规模海上风电场。如开发其中15%的风能资源,即可兴建一个相当于年产4250×104t标煤、每年减排二氧化碳1.12×108t的永续绿色能源基地,而且不占用一亩耕地,不产生一个移民,也不存在生态安全问题。由于风能的自身特性,导致风电的波动性、间歇性和不规则性,使电网难以承受海上大规模风电场的巨大电能。建议采用非并网风电技术,在辐射沙洲地区建设若干"低碳型"高耗能绿色工业园区,利用风能替代化石能源,实现"高碳能源向无碳能源"的跨越。如海水淡化产业基地,变输电上岸为输水上岸;氯碱生产基地及PVC等衍生产业;以电解铝为重点的有色冶金产业基地;新型绿色煤化工产业基地等。     

Numerical analysis of heat transfer in arbitrary plane domains using a novel Trefftz energy method

In this article, we first propose a novel Trefftz energy method (TEM) for the numerical analysis of heat transfer in arbitrary plane domains. The TEM introduces the Trefftz energy bases in the complete linear space to approximate the numerical solution of the mixed boundary value problem in the heat transfer over an arbitrary plane domain. The Trefftz energy bases not only satisfy the Laplace equation but also preserve the energy, whose performance is better than the original Trefftz bases. Three benchmark numerical examples are tested to demonstrate the efficiency and accuracy of the proposed TEM. Although the multiple-scale Trefftz method can treat these problems with high accuracy, the TEM can further raise the accuracy with one order. Therefore, the present scheme is a competitive alternative to existing methods for solving heat transfer problems in arbitrary plane domains.     

中国煤炭基地水与能源协同发展评估

鉴于中国煤电生产主要集中于黄河中、上游和西北内陆河流域,水资源极为紧缺,扩大火电规模势必加重当地的水资源压力,进而带来严重的生态环境问题。基于全国14大煤炭基地的发展规划和最严格水资源管理制度的用水总量控制指标,分析2020年煤炭基地的火电发展是否超出当地的水资源支撑能力。结果显示,到2020年14大煤炭基地新增燃煤发电的用水量为19.32×108 m3,煤炭基地的新增可供水资源量为45×108 m3,大部分煤炭基地可通过新建水源工程、水源置换等途径满足需求,但神东、晋东、黄陇、河南等四大煤炭基地的新增可供水量不能满足新增煤电用水需求,需要根据当地水资源情况合理控制火电资源开发,该结论为实现水与能源的协同管理提供了依据。     

别墅建筑暖通节能及太阳能应用设计研究

本文以北京某别墅太阳能供暖及空调设计为例，通过太阳能的得热计算、建筑冷热负荷计算及供暖空调方案的分析选择，提出了一种节能舒适的应用天然能源的设计思路。     

某中速柴油机底座刚度对整机模态影响分析

某型中速柴油机在试车台测试时振动偏大,初步判定系柴油机底座刚度不足引起.对柴油机底座进行改进设计,在此基础上对不同方案的底座进行刚度计算和模态分析,然后对不同底座方案整机进行模态计算,得到底座刚度与整机振动模态间的关系.同时分析了采用不同垫板对整机模态的影响,为柴油机底座的选型设计提供参考.     

水电站蓝水足迹的计算分析与探讨

为合理评估水电开发利用过程消耗水资源的问题,计算了我国已建283座大中型水电站的总蓝水足迹及其平均值,同时根据气候区域及水电基地的不同将这些水电站划分为7个气候分区和13个水电基地,并分别计算其平均蓝水足迹。结果表明,由于气候分区及所在水电基地的不同,所统计水电站的平均蓝水足迹差异较大,但总体上平均蓝水足迹较小。通过分析计算结果合理性及敏感性,得出水电站蓝水足迹的变化主要取决于水电站和水库的参数。说明蓝水足迹可作为水电站规划与运行期间的一个指标,为我国水资源的科学管理及合理开发提供了理论依据。     

我国风电整机生产基地发展近况

虽然产能有所过剩,但由于地方政府采取了以资源换税收的政策,仍使得整机生产基地的数量在不断增加。本文对我国整机生产基地的近期情况做了简单介绍,并对未来整机生产基地的发展方向做了调研与分析。     

Value-at-risk estimation of crude oil price using MCA based transient risk modeling approach

With the increasing level of volatility in the crude oil market, the transient data feature becomes more prevalent in the market and is no longer ignorable during the risk measurement process. Since there are multiple representations for these transient data features using a set of bases available, the sparsity measure based Morphological Component Analysis (MCA) model is proposed in this paper to find the optimal combinations of representations to model these transient data features. Therefore, this paper proposes a MCA based hybrid methodology for analyzing and forecasting the risk evolution in the crude oil market. The underlying transient data components with distinct behaviors are extracted and analyzed using MCA model. The proposed algorithm incorporates these transient data features to adjust for conservative risk estimates from traditional approach based on normal market condition during its risk measurement process. The reliability and stability of Value at Risk (VaR) estimated improve as a result of finer modeling procedure in the multi frequency and time domain while maintaining competent accuracy level, as supported by empirical studies in the representative West Taxes Intermediate (WTI) and Brent crude oil market.     

Sweet sorghum for bioethanol production: Crop responses to different water stress levels

Cultivation of sweet sorghum for the production of bioenergy is an attractive option to cope with the challenges of climate change and variability. In fact, on one hand it represents an interesting strategy of mitigation and, on the other, the use of drought resistant species could be considered as an opportunity of adaptation to the change of precipitation patterns. Anyway, when considering the production of agricultural feed stocks, particular attention should be addressed to the environmental sustainability of field production in order to avoid trade-offs in relation to food production, land use and pressure on the water resources. In this context, the cultivation of drought-tolerant energy crops as sweet sorghum (Sorghum vulgare (L.) var. Saccharatum) could be an interesting option. On the bases of these considerations, the current study had the aims i) to monitor the sweet sorghum growth and productive responses to different water treatments, in order to assess the extent of tolerance to constant water stress and ii) to assess the potential for first and second-generation bioethanol production obtainable from soluble sugars and residual biomass at two different development stages, flowering and physiological maturity.Results show that the length of the growing period should be decided on the bases of the objective pursued.If the objective is just the production of bioethanol, a longer cultivation period could be more suitable, but, on the contrary, if the objective is more addressed to an optimization of water, flowering should be considered the best harvest time.     

Facile and eco-friendly synthesis of porous carbon nanosheets as ideal platform for stabilizing rhodium nanoparticles in efficient hydrolysis of ammonia borane

Carbon materials have been demonstrated as excellent carriers for preparing supported metal nanocatalysts in catalytic applications. However, numerous chemical activators including strong acids and bases were applied, leading to the entire process dangerous and hazardous. Eco-friendly, economic, and convenient synthesis of carbon materials with desired properties as supports for metal nanoparticle (NP) stabilization to boost performance is important but remains challenging. Here, we developed a facile and eco-friendly strategy to synthesize porous carbon nanosheets (PCNs) with ultrahigh specific surface area (2575.1 m²/g) via pyrolysis the mixture of potassium oxalate and glucose. The resultant PCNs can be used as ideal platform for in-situ distribution of small Rh NPs (Rh/PCNs) as efficient catalysts in hydrogen production from ammonia borane (AB) under ambient conditions. Specifically, Rh/PCNs displayed high activity for AB hydrolysis, with a turnover frequency (TOF) of 513.2 min⁻¹. Small and well-distributed Rh NPs on PCNs with large catalytically active surface atoms are contributed to the high catalytic property of Rh/PCNs for the reaction. Present study has demonstrated that the PCNs is a superior catalyst support for preparing a series of metal NPs in other catalytic applications beyond hydrolysis reaction.     

Temperature-dependent properties of organic-on-inorganic Ag/p-CuPc/n-GaAs/Ag photoelectric cell

A thin organic film of copper phthalocynanine (CuPc) as p-type semiconductor was deposited by vacuum evaporation on n-type GaAs single-crystal semiconductor substrate. Electrical, photoelectrical and frequency response of the cells were investigated at a temperature interval of 23–74 °C. Photoelectric characteristics were measured under semiconductor laser beam injection illumination (), while frequency response was investigated by laser beam modulated with a frequency range of 10 Hz–100 kHz.It was observed that cell parameters such as rectification ratio; threshold voltage; nonlinearity coefficient; junction, shunt and series resistances; diode ideality factor and power conversion efficiency were temperature-dependent. Moreover, experimental data showed that open-circuit voltage decreases with an increase in frequency whereas short-circuit AC current falls with frequency but remains constant as a function of temperature. It was further observed that the short-circuit DC current remained constant with an increase in frequency as well as temperature. Based on the experimental data an equivalent circuit of photoelectric cell was proposed to explain the observed behavior.     

Fluctuations in instantaneous clearness index: Analysis and statistics

Solar radiation is characterized by short fluctuations introduced by passing clouds. An analysis of these fluctuations with regard to solar energy applications should focus on the instantaneous clearness index. Its probability distribution for a given mean clearness index is, as a first approximation, independent from the season and partly also from the site. This is verified for four annual datasets from three different sites.An analysis of fluctuations in solar radiation must focus on their amplitude, persistence, and frequency of occurrence rather than their location in time. The Fourier analysis cannot satisfactorily provide this information since time series of the instantaneous clearness index exhibit no periodicity. Instead, a localized spectral analysis based on wavelet bases rather than on periodic-ones has been applied. This analysis allows the decomposition of the fluctuating clearness index signal into a set of orthonormal subsignals. Each of them represents one specific scale of persistence of the fluctuation.The annual mean square values of all subsignals have been analysed, permitting the allocation of the signal’s power content to the different scales of persistence of a fluctuation. These annual mean values agree well for the different datasets, indicating the existence of statistically significant mean square values of the fluctuations as a function of their persistence.The analysis offers a valuable tool for the estimation of power flow fluctuations introduced by direct solar energy systems. With further elaboration it may be applied by power system operators for network planning in distribution grids with a high density of embedded generation.